Traditionally there are 12 birthstones, each associated with one month of the year. Each month is assigned a particular crystal or gemstone. In modern times, more gemstones have been added to the list. Nowadays, birthstones are also categorised according to Zodiac sign. Birthstones are said to resonate with or enhance the qualities of those born under a particular Zodiac sign or month. Below, we have divided our birthstones by Zodiac sign as well as linking to the traditional birthstones of that month.